Related Stories

Why, might you ask, should anyone want to celebrate a mathematical constant which allows you to calculate the area inside a circle?

As obscure as it seems, the number pi, or 3.14159… has been crucial to the development of modern life. As far back as the ancient civilisations of Babylon and Egypt, people needed approximations of pi to estimate the flooding of the Tigris, Euphrates and Nile rivers, for astronomy, and for surveying and building ziggurats and pyramids.

Today, 4000 years after people first discovered how useful pi could be, we are about to celebrate International Pi Day.

The first time a day was dedicated to pi was on March 14, 1989 at the Exploratorium science centre in San Francisco.

The idea was the brainchild of Larry Shaw, a physicist at the centre. Since then, this museum and many others, as well as universities, schools and individuals have celebrated Pi Day by performing pi-related activities; creating pi puns; baking, throwing and eating pies; and singing pi songs.

The date is derived from the first three numbers of pi — 3.14 — using the American way of expressing the date, just as September 11 is called 9/11. At first Pi Day was a gimmick and a bit of a joke, but now it is a big deal. Many North American schools use it to spark interest in maths and science projects (for example, calculating the area of real baked pies and then eating them).

What is Pi? Pi is represented by the Greek letter π, and it is the most important constant in mathematics. You can find out the area of a circle of radius r, using πr2. The perimeter of this circle would have the length 2πr. Without pi there is no theory of motion and no understanding of geometry. Likewise, the volume of a sphere of radius r is 4/3πr3 and that of a cylinder of height h is πr2h. Pi occurs in important fields of applied mathematics such as Fourier analysis. It is used throughout engineering, science and medicine and is studied for its own sake in number theory.

Pi goes global

Public interest in pi came to a head in 2009 when the US House of Representatives formally declared March 14 National Pi Day, in House Resolution number 224. The Bill grandly begins: "Whereas the Greek letter (pi) is the symbol for the ratio of the circumference of a circle to its diameter…". After many more "whereases", it resolves … "That the House of Representatives (1) supports the designation of a Pi Day and its celebration around the world". The Bill urges schools and educators to help learn about pi and generally engage students in the study of mathematics.

The growing interest in pi has seen it become firmly established in popular culture. Pi has been featured in such TV shows as The Simpsons and Star Trek , as the title of a Kate Bush song, in the movies The Matrix, and Pi; and in the 2001 novel Life of Pi by Yann Martel.

Pi has even inspired the invention of a new literary form called 'piems'. The challenge is to write a poem where the length of each word is the same as the number in the pi sequence. For example, the first eight decimal places of pi can be recalled with the phrase: "How I need a drink, alcoholic of course." (to represent 3.1415926).

If you're better with numbers than words, some folks prefer to memorise pi for themselves. The current Guinness World Record for remembering pi is well in excess of 60,000 digits. If you want to give it a try, memorisers typically add 10 or 15 digits a day to their total.

Meanwhile, the world's top mathematicians continue to outdo each other, calculating pi to ever more decimal places. The current world record is five trillion (5,000,000,000,000) digits. It was set in August last year by Japanese systems engineer Shigeru Kondo, using an $18,000 homemade computer running software developed by American university student Alex Ye.

Irrational attraction

But just as climbers still climb Mount Everest, this is certainly not the end. Within the next ten years, a quadrillion digits will probably have been computed.

What makes it really interesting is that pi is an irrational number, so its digits never terminate or repeat. While it never runs dry, we cannot prove that the decimal expansion of pi is normal, athough it most probably is (in other words it has equally many ones, twos, threes, etc).

While it is very likely we will learn nothing new mathematically about pi from computations to come, we just may discover something truly startling. That was part of the punch line in astronomer Carl Sagan's novel Contact, when he suggested that alien life forms encoded messages to the human race in the decimal places of pi.

Stay tuned!

About the author Professor Jonathan Borwein is a world expert on pi. He was dubbed `Dr Pi' after he and his brother Peter developed algorithms (computer formulae) that enabled extremely fast calculations of pi. These algorithms today allow new world records to be set in calculating the value of pi using super-fast computers.